The utilization of hermetically and semi-hermetically sealed motor-compressor units has become increasingly prevalent in recent years in refrigeration applications wherein the motor-compressor unit is employed to compress a refrigerant vapor. The compressor is generally driven by an electric motor, and the crankshaft of the compressor typically rotates at relatively high speeds. As is obvious, at relatively high operating speeds, proper lubrication of the crankshaft, journals, bearings and of other moving parts of the compressor is highly critical. Generally, lubricant such as oil is stored in a reservoir or sump in the casing of the motor-compressor unit, and an oil pump is employed to pump oil from the sump through the compressor to lubricate the moving parts thereof. Generally, when a hermetic or semi-hermetic motor-compressor unit is employed in a refrigeration circuit, the lubricating oil is miscible with the refrigerant vapor. A portion of the oil pumped through the compressor becomes entrained with the refrigerant passing therethrough, and the entrained oil circulates through the refrigeration circuit with the refrigerant.
A terminal assembly is provided to supply electric power through the casing of the hermetic compressor. The terminal assembly comprises a body member welded or otherwise secured to the compressor casing and has a plurality of conductor pins secured to and extending through the body member such that one end of each pin is located within the casing while the other end extends outside of the casing. Electrical insulating and sealing material such as glass or epoxy potting forms a hermetic seal between each pin and the body member. The internal end of each pin is connected in any suitable conventional manner to the electrical leads of the motor for driving the compressor. The external end of each pin is connected to a suitable source of power in any suitable conventional manner. Typically, a cover is provided over the external pins and their connections.
The diameters of the pins are so small, about one eighth inch, that the operating pressures acting on the internal ends of the pins produce maximum forces on the order of five pounds acting on each of the pins. However, if the glass or epoxy bond of one of the pins becomes broken or damaged, the pin with the damaged seal may be dislodged from the terminal assembly permitting rapid leakage of refrigerant and oil.